I linked to an article by Theodore Calmes back in Issue 119 about implementing clustering of annotation points inside MapKit. Claus Höfele has taken the code from that article and turned it into a component which can be easily integrated into any view controller providing the same functionality from the original article. Great work.
Justin DeWind with a practical example of implementing some basic Reactive Cocoa magic into an app. He uses the example of replacing the UISearchBar delegate with RAC signals and walks through every step in a very understandable way. If you have been struggling to get on board with Reactive Cocoa then this walk through gives a gentle introduction by way of something you will already be very familiar with.
Brad Grzesiak on applying the single responsibility principle when developing for iOS. Especially in view controller code, it can be very easy to let it slip away from you and end up in Massive View Controller land. If you are tying to pursue that noble goal then this article will be of interest.
We have a wonderful array of animation techniques on iOS but with every extra API comes more questions about whether you are "doing it right". I would happily read every word that David Rönnqvist writes about animation code but this article should be made essential reading if you are working with Core Animation code. Oh and if you're reading this David, I wouldn't have been able to resist calling that section "avoid removedOnCompletion = NO".